Iodine,chlorine or bromine stabilized olefin polymers

ABSTRACT

OLEFIN POLYMERS ARE STABILIZED TO MINIMIZE MELT FLOW DROP OFF AT ELEVATED TEMPERATURES BY ADMIXING THE POL YMER WITH 0.004 TO 0.5 WEIGHT PERCENT OF ELEMENTARY IODINE, CHLORINE OR BROMINE, RESULTING IN IMPROVED PROCESSABILITY.

US. Cl. 260-455 United States Patent 'IODINE, CHLORINE 0R BROMINESTABILIZED OLEFIN POLYMERS Clive D. Moon, Bartlesville, 0kla., assignorto Phillips Petroleum Company, a corporation of Delaware No Drawing.Filed Oct. 7, 1968, Ser. No. 765,660

' Int. Cl. 'C08f 45/56 4 Claims ABSTRACT OF THE DISCLOSURE sability.

y This invention relates to a method for stabilizing olefin polymers. Inanother aspect, this invention relates to olefin polymers which arestabilized against melt flow drop off at elevated temperature.

I Normally, polymers and other plastic materials prepared from olefinsare processed by heating the material to 'atemperature level where theybecome molten and then shaping the molten polymer into the desired formby various techniques such as extruding, injection molding, blow moldingand other types of thermoforming. At these high temperatures, manypolymers demonstrate a melt flow drop off which causes problems in theproduction of the polymer, as well as in fabrication. For example,thetimes for various molding processes are in creased because of thelonger time required by the less fiuid polymer to fill the molds.

Briefly, melt flow is the amount, in grams for ten minutes, of a resinthat can be forced through an orifice,

when subjected to a given force at a given temperature. Melt flow dropolf is a decrease in the melt flow from time interval to time interval,usually reaching a relatively constant melt flow. Naturally, if the dropofi is too great, the resin will cease to flow or How slowly, resultingin the above-mentioned problems.

- The polymer is often processed into pellets by extrusion techniques. Amelt fiow drop oif during this processing results in flow.characteristic changes which can limit the potential applications forthe processed polymer. Also, in applications where clearness is desired,e.g. film manufacture, it is important that the stabilized polymer haveminimum discoloration.

Various methods for stabilizing these polymers have met with varyingdegrees of success, and many attempts have been made to find improvedmethods for stabilizing these polymers.

- I have discovered that olefin polymers can be stabilized against meltflow drop olf at elevated temperatures by admixing the polymer with verysmall amounts of elementary iodine, chlorine or bromine. I havediscovered that very small amounts of these halogens, when reacted withthe polymer, are quite effective in decreasing the melt flow drop olfwith substantially no effect on the physical properties of thestabilized polymer. I have also discovered that melt flow stability ofthese polymers can be obtained without inducing any undesirablediscoloration to the polymer. The processability of these stabilizedpolymers is also improved by this invention.

Accordingly, an object of this invention is to provide "ice an improvedmethod for stabilizing olefin polymers against melt flow drop off duringhot processing. Another object of this invention is to provide animproved method for stabilizing olefin polymers against melt flow dropoff with little discoloration to the stabilized polymer. A furtherobject of this invention is to provide an olefin polymer compositioncapable of being hot processed with little or no decrease in melt flow.

Other objects, aspects and advantages of my invention will becomeapparent to one skilled in the art from the following disclosure andclaims.

In my invention, olefin polymers are stabilized to minimize melt flowdrop off at elevated temperatures by admixing the polymer with 0.004 to0.5 weight percent of elementary iodine, chlorine or bromine, based onthe total weight of the polymer and the stabilizing additive.

When minimum discoloration of the stabilized polymer is desired, lesseramounts of stabilizing additive can be added to the polymer. Higherconcentrations of stabilizing additive are satisfactory for minimizingmelt flow drop 011. When the stabilizing additive is a liquid, theadditive and polymer are mxed thoroughly, e.g., by shaking in a vessel.

The stabilizing additives can be added to the polymer by any suitablemeans which effects a homogeneous distribution of the additive in thepolymer. The stabilizing additive can be mixed with the polymer in anyparticulate form, such as granular, pellet, powder, or flufi, by me--chanical mixing techniques such as blending, milling or kneading withdevices such as a Henschel mixer, a Banbury mixer, a BrabenderPlastograph, a Waring Blendor, a roll mill and the like.

Iodine or bromine can also be dissolved in inert solvents such aschloroform, carbon tetrachloride, hydrocarbons such as pentane, hexane,heptane, Stoddards solvent or mixtures of hydrocarbons, benzene, tolueneand the like, and mixing the polymer with the resultant solution. Thesolvent can be subsequently removed by heating, purging with air, or thelike. Chlorine gas or liquid bromine can also be used. When chlorine isthe stabilizing additive, the reaction temperature should be in a rangeof room temperature to 120 C., preferably to C.

The stabilizing additives can be effectively employed in olefin polymerswhich are subject to melt flow drop off. The term polymer as herein useddesignates either homopolymers, copolymers or blends thereof. Thisinvention is especially elfect'ive with polymers of l-olefins having 2to 8 carbon atoms per molecule. Specific examples of homopolymers arehomopolymers of ethylene, propylene, butene-l, pentene-l,4-methyl-pentene-l, hexene-l, heptene-l, octene-l and the like. Specificexamples of copolymers are copolymers of ethylene and propylene, ofethylene and butene-l, of propylene and butene-l, ethylene and hexene-l,propylene and octene-l, ethylene and 4-methylpentene-1, ethylene andoctene-l, hexene-l and octene-l and the like.

The olefin polymers capable of being stabilized in accordance with thisinvention can be made by any of the various'known polymerizationprocesses. For example, polymers prepared by the polymerization processdescribed in US. Pat. 2,825,721, Hogan et al. (1958), and British Pat.853,414, Phillips Petroleum Company (1960), can be stabilized with theadditives of this invention. Polymers made by the high pressure processor with organometal catalyst systems are examples of other polymers thatcan also be used. The polymer to be stabilized can contain otheradditives such as stress-cracking in- 3 4 hibitors, antioxidants,fillers, pigments, cross-linl ing TABLE III agents, plasticizers, andthe like. The stabilizing additives W I I V P N t of this invention areeffective with or without these other ggfi li f gggfg? g}; g fggadditives. sated time interval, in melt flow The advantages of myinvention are further illustrated 5 Cmwmtmum, (,fbrmmm, by the followingexamples. The reactants, proportions and wt iwrwlt 10 15' minutes otherspecific conditions are presented as being typical and 0 Q15 07 a 06 O473. 3 should not be construed to limit the invention unduly. 0.000 0.100.10 0.10 33.3

0.000 0.11 0.10 .12 0.0i2 0.13 0.14 EXAMPLE I m 0.023 0.13 0.15 0.1:;35.0 Samples were prepared from polyethylene made by the M46 0 14particleform process of British Pat. 853,414 using a chromiumoxide-containing catalyst. The polymer had a melt A i the first twoexamples, a treatment with a very indeX 0f (ASTM D 123862T, Conditionsmall amount of halogen, in this case bromine, minimizes E) and adensity of 0.96 g./cc. (ASTM D 1505-63T). 1 melt flow drop olf. Thepolymer fluff was slurried with a solution of iodine in normal hexanefor about 3 minutes in a stirred con- EXAMPLE 1V tainer. The solvent wasallowed to evaporate and the ffuff was blended for 3 minutes on aBrabender Plastograph Polyethy p Were Prepared y meterlng a The meltflow drop off Was determined by measuring the 20 l y amount of chlorlnegas i a stoppered bottle amount of polymer extruded through the orificeof the talnmg the P y at a reactlon tempefature of 95 o melt indexer at550 F. during consecutive S-minute in- The P y Was Plastogfaphedmlmltfis at 190 tervals, using a piston load of 2200 grams. One samplewith The melt flow p 03 t determlned as In Example no iodine additivewas used as a control. The results are One sample 'with no chlorine wasused as a Control. The shown in Table I. -3 results are shown in TableIV.

TABLE I Percent Weight of polymer extruded, decrease in grams, forindicated time, innielt flow terval, min. between Concentration of 5 and25 iodine, wt. percent Color 0.5 5-10 10 15 1520 20-25 minutes 0(control) White 0.08 0. 04 0.03 0.03 0.03 02.5 0.0 5 Slightly pink 0. 270.24 0. 25 0. 25 0. 25 7.4 0. (10. 0.40 0. 30 0. 30 0. 30 0. 30 10.0

stability provided by the process.

The data show that very small amounts of iodine treat- TABLE [V meritsubstantially improves melt flow drop off in the r 1 Weight of polymereX- Percent P y truded, grams, for indidecrease EXAMPLE II cated timeinterval, in ngelt flow min. et-ween Concentration of bromine 5 and 25Polyethylene samples were prepared as in Example I. wt. percent 5 s1010-15 15-20 minutes The polymer fiuft was mixed with elementary solidiodlne 0 17 0 O9 0' 09 09 0 in a closed container on a drum roller for 1to 2 hours. 0. 0.24 0.23 17.8 The melt flow drop ofi? was determined onpellets extruded gg 8- at 500 F. as in Example I. One sample with noiodine 0.13 0. 45 0.48 0. 4s 0. 40 was used as a control. The resultsare shown in Table 11.

TABLE II Percent Weight of polymer extruded, decrease in giams, forindicated time, inmelt flow terval, min. between Concentration of 5 and25 iodine, \vt. percent- Color 0 5 5 10 10-15 15-20 20-25 minutes 0(control) .1 White 0. 08 0.04 0.03 62. 5 0.004"... d0 0. 27 0. 23 0. 230. 24 0. 24 ll. 0 0.007 do 0. 34 0. 30 0. 30 0. 30 0. 30 11. 8

1 Data was not collected after this point as the test was terminatedafter l5 minutes.

As in Example I, a very small amount of iodine substantially improvesmelt flow drop off in the polymer.

EXAMPLE III Polyethylene samples were prepared as in Example I. Thepolymer was placed in a glass container followed by the addition ofliquid bromine. After thorough shaking and evaporation of any liquid,the reaction mixture was allowed to stand overnight. The melt flow dropoff was determined on pellets extruded at 550 F. as in Example I. Onesample with no bromine was used as a control. The results are shown inTable III.

3. The composition of claim 1 wherein said polymer is a polymer ofethylene or propylene.

4. The composition of claim 3 wherein said polymer is 2,449,970 9/1948Borglin 260-80 2,955,099 10/1960 Mallouk et a1. 260-45] 6 3,134,7475/1964 Amos et a1 260-45] 3,223,664 12/ '1965 Conlon 260-291 3,372,1403/1968 Witt 260-459 DONALD E. CZAJA, Primary Examiner R. A. WHITE,Assistant Examiner US. Cl. X.R. 260-949

